In the formation of glass fibers various bushings have been described in the prior art for forming glass fibers under high pressures. Typical of such patents are U.S. Pat. Nos. 3,573,014; 3,574,581 and 3,625,025. In the processes described in the aforementioned patents special bushing configurations generally of a tubular shape are utilized in conjunction with high pressure forming equipment such as special pumps as described in U.S. Pat. No. 3,733,188 which permit the formation of glass fibers under high pressure conditions. These processes are valuable in that fine filament fibers can be produced at considerably reduced tensions. The utilization of fiber glass bushings having a folded configuration are also shown in the aforementioned U.S. Pat. No. 3,574,581.
While processes such as those described in the prior art permit the skilled artisan to produce fibers from molten glass under pressurized conditions some difficulties are encountered in utilizing these processes because of the necessity to adapt the specialized equipment described in these patents to a conventional glass fiber forming forehearth. Thus in a normal fiber glass operation a glass melting device or furnace is provided which is utilized to melt the glass batch ingredients into molten glass form. The molten glass then in a conventional operation flows from the furnace area through a small refining area into an elongated forehearth which may take any one of several configurations in a fiber glass direct melt operation. A direct melt system is one in which the glass batch ingredients are melted in a single furnace and fed to an elongated forehearth to which several glass fiber forming bushings are attached. Special adaptations of the forehearth are required in order to permit operations utilizing the high pressure pumping equipment and special configuration bushings which are described in the aforementioned patents. Typical forehearths of the character utilized in industry today as described in the publication "The Manufacturing Technology of Continuous Glass Fibers" by K. H. Loewenstein, Elsevier Scientific Publishing Company, New York, 1973 at pages 61-70.
Thus, a need still exists in the industry for the production of fibers under pressures from a conventional direct melt forehearth which will enable one skilled in the art to utilize conventional direct melting and forehearth technology while still providing the advantages inherent in the production of glass fibers under pressure such as has been described by the prior art in the aforementioned U.S. Patents. In accordance with the instant invention a fiber glass forming bushing is provided which permits the utilization of fiber glass bushings in conventional forehearths utilizing either pumping means or other methods of applying pressure to the glass for the production of glass filaments under high pressure.